Method of increasing the rate of heat transfer



Feb. 27, 1968 w. B. DAILY E L 7 I METHOD OF INCREASING THE RATE OF HEATTRANSFER Filed Dec. 28, 1965 38 ,la" UUUEJEEIEJ UEIUEHEE] EIUE1- EUEEIEBEE BEBE INVENTORS [710 J dfaeaa v awry/[M59675 United States Patent3,370,644 METHOD OF INCREASING THE RATE OF HEAT TRANSFER William B.Daily, and Elio J. Speca, Wellsville, N.Y., as-

signors to The Air Preheater Company, Inc., New York,

N.Y., a corporation of Delaware Filed Dec. 28, 1965, Ser. No. 516,936 1Claim. (Cl. 165-1) ABSTRACT OF .THE DISCLOSURE The method of increasingthe rate of heat transfer between fluids in a heat exchanger byelectronically increasing the circulation within a fluid andsimultaneously removing particulate matter therefrom withoutmechanically increasing the resistance of the passageways to the flow offluid therethrough.

This invention relates generally to heat exchangers, and particularly toa method by which the heat transfer rate of a recuperative heatexchanger may be substantially increased.

Fluids flowing through passageways in heat exchangers tend to stratifyand produce zones of laminar flow which insulate rather than promote thetransfer of heat. Consequently heat exchangers constructed according toconventional heat exchanger standards frequently assume largeproportions as a compensation for their low coefficient of heattransfer. To overcome this objection as to size and low heat transfercoefl'icient various forms of extended surface have been placed in theheat exchanger along the walls of the heating fluid or the fluid to beheated. Such extended surface means disrupt the laminar flow and createa degree of turbulence that enhances the rate of heat transfer but alsoincrease the resistance of the passageways to the flow of fluidtherethrough.

Thus an optimum design of heat exchange equipment would affordsimultaneously a maximum rate of heat transfer and a minimum resistanceto the flow of fluids therethrough, and this invention therefore has forits principal object the provision of a heat exchange device that has ahigh rate of heat transfer and a low resistance to the flow of a fluid.

According to the invention it has been discovered that 4 zones ofstratified fluid flow may be disrupted without substantial variation inthe resistance to the flow of fluid therethrough by causing an ionicdischarge to traverse the several stratifled layers of fluid flow. Themanner that this discovery has been applied to the invention at hand maybe more readily understood by referring to the accompanying drawings inwhich:

FIGURE 1 is a sectional elevation of the heat exchanger according to theinvention.

FIGURE 2 is a horizontal section of FIGURE 1 as seen from 2-2, and

FIGURE 3 is a horizontal section of a modified form of heat exchanger.

A heat exchanger embodying the present invention is shown in FIGURE 1wherein a heating fluid admitted to a housing through an inlet 12 isdirected through grounded tubes 14 to an outlet 16 and a connectedexhaust duct. A fluid to be heated is admitted to the housing through aninlet port 22 where it flows around the tubes 14 to receive heat fromthe heating fluid inside said tubes before it is exhausted to the outletport 26 as a heated fluid.

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The tubes 14 extend axially through the housing 10 between aperturedtube sheets 28 and 34 having one or more baflle plates 36 preferablypositioned therebetween to effectively increase the dwell period of anyfluid passing over the tubes between inlet and outlet ducts. Each tube14 contains a centrally mounted discharge electrode 38 supported byinsulators 40 which electrically isolate the electrodes 38 from thegrounded tubes 14. The discharge electrodes 38 are themselveselectrically charged by being connected to a suitable source 42 of highvoltage direct current, and then discharged across the space whichsurrounds each electrode to the grounded tubes 14. As the flow of ionsmoves from the discharge electrode 38 to the grounded tube 14 anelectric Wind is produced transversely with respect to inlet and outletports so as to increase the turbulence of the fluid inside the tubes andto preclude conditions of laminar flow. Inasmuch as laminar flowconditions are obviated without the necessity of placing extendedsurface means in the fluid stream, there is an increase of heat transferwithout a corresponding increase in pressure drop of the fluid.

FIGURE 3 shows a modified form of the invention wherein the tubes of thedesign illustrated in FIGURES 1 and 2 have been replaced by plates 44spaced apart according to a predetermined plan to provide alternateinter-plate passageways 14 and 48 for the heating fluid and the fluid tobe heated. Ionic discharge electrodes 38 may be subsequently positionedin the passageways for one or both of the fluids in accordance with theforegoing disclosure to increase the rate of heat transfer of theseveral fluids.

While this invention has been described with reference to the severalembodiments illustrated in the drawing it is evident that variouschanges may be made without departing from the spirit of the invention,and it is intended that all matter contained in the above description orshown in the accompanying drawings shall be interpreted as illustrativeand not in a limiting sense.

We claim:

1. The method of increasing the rate of heat transfer between a heatingfluid and a fluid to be heated in a heat exchanger having a housing withsurface members forming walls between passageways for said fluids andopenings which comprise inlet and outlet ports for said fluids flowingthrough said passageways, said method comprising the steps ofelectrically grounding said wall forming surface members, effecting adischarge of ions in the passageway for at least one of said fluids tosimultaneously ionize the fluid it traverses and the particulate matterentrained therein so as to attract the ionized particles to the groundedsurface, and periodically terminating the discharge of ions to permitfluid flowing through said passageways to flow directly therethrough andremove deposits from said wall forming surface members.

References Cited UNITED STATES PATENTS 1,916,337 7/1933 Schmidt 165-12,605,377 7/1952 Kaehni et a1. 1651 FOREIGN PATENTS 373,051 4/1923Germany.

ROBERT A. OLEARY, Primary Examiner.

CHARLES SUKALO, Examiner.

